This application relates generally to vehicles having a combination starter-generator. More specifically, this application relates to tensioning systems and drives for combination starter-generators.
Prior internal combustion engine includes both a starter machine and a generator or alternator machine (hereinafter generator). The starter provides an engine-cranking torque to the flywheel or crankshaft of the engine in order to rotate the camshaft and facilitate the movement of the pistons during the ignition of the engine. The generator provides an electrical output in order to meet the electrical loads of the vehicle, as well as to charge the vehicle""s battery. Generally, a torque is applied to a pulley of the generator by a belt frictionally engaged with a pulley of the generator and a pulley of the engine in order to generate the electrical charge from the generator.
The concept of using only one machine to do both functions, namely starting and generating, adds efficiency. Thus, starter-generators use less space, weigh less, eliminate the cost of one of the machines and reduce assembly time. However, starter-generators give rise to issues described below that affect the cost, complexity, and reliability of such starter-generator systems. Accordingly, there is a continuing need for inexpensive, reliable tensioning systems for starter-generators.
A combination starter-generator system for use in a vehicle having an internal combustion engine is provided. A drive mechanism connects the starter-generator machine and the internal combustion engine. The starter-generator machine generates a current by receiving a charging torque from one side of the drive mechanism and starts the internal combustion engine by imparting a starting torque to a different side of the drive mechanism. Depending on the application, the charging torque or the starting torque is a greater torque. A passive tensioning system cooperates with the drive mechanism to tension the drive mechanism only at the side of the greater torque.
An apparatus for starting an internal combustion engine having a starter-generator machine is provided. The starter-generator machine is operable in a first direction for generating a current and a second direction for starting the internal combustion engine. A drive mechanism connects the starter-generator machine and the internal combustion engine by a non-adjusting gear ratio in a range between 2:1 to 3:1. The starter-generator machine operates in the first direction to generate a current by receiving a charging torque from the internal combustion engine imparted to a first side of the drive mechanism. The starter-generator machine operates in the second direction to start the internal combustion engine by imparting a starting torque to a second side of the drive mechanism. A first tensioning system cooperates with the drive mechanism to tension the drive mechanism at the first side during application of the charging torque. A second tensioning system cooperates with the drive mechanism to tension the drive mechanism at the second side during application of the starting torque.
An active tensioning system for use on a drive mechanism is provided. The drive mechanism creates a first slack side and a first tight side of the drive mechanism. The drive mechanism also creates a second slack side and a second slack side of the drive mechanism. The first slack side and the second tight side are coincident. Similarly, the second slack side and the first tight side are coincident. The active tensioning system has a guide. A first idler sprocket is operatively coupled with the first slack side of the drive mechanism and is slidable on the guide. A second idler sprocket is operatively coupled with the second slack side of the drive mechanism and is also slidable on the guide. A spring connects the first idler sprocket and the second idler sprocket. The spring also biases the first idler sprocket and the second idler sprocket towards one another such that upon creation of the first slack side and the first tight side, the first tight side acts upon the second idler sprocket to slide the first idler sprocket and the second idler sprocket upon the guide to tension the drive mechanism, and such that upon creation of the second slack side and the second tight side, the second tight side acts upon the first idler sprocket to slide the first idler sprocket and the second idler sprocket upon the guide to tension the drive mechanism.
A combination starter-generator system is provided. The vehicle has an internal combustion engine and a starter-generator machine for generating a current and starting the internal combustion engine. A drive mechanism connects the starter-generator machine and the internal combustion engine. The starter-generator machine charges the battery by receiving a charging torque from a first side of the drive mechanism. The starter-generator machine starts the internal combustion engine by imparting a starting torque to a second side of the drive mechanism. The drive mechanism compensates for differences in the charging torque and the starting torque with a non-adjusting gear ratio in a range between 2:1 to 3:1. An active tensioning system cooperating with the drive mechanism to tension the drive mechanism at the first side during application of the charging torque or at the second side during application of the starting torque.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.